Embodiments of the present invention relate to an anti-fuse of a semiconductor device, and more particularly to an anti-fuse using a Field Nitride Trap (FNT).
Semiconductor devices cannot be used as memory devices when a defect or failure occurs in at least one unit cell therein during a fabrication process. A memory device having at least one failed unit cell is classified as a defective product, and results in decreased production efficiency. Therefore, a technology of substituting a defective cell with a redundancy cell has been introduced so as to repair the defective cell in the memory device.
For example, if a defective cell is detected in a test operation after a memory device is fabricated, a program operation for making access to a redundancy cell with an address input to access to the defective cell is carried out in an internal circuit of the memory device. Therefore, if an address signal corresponding to a defective line used to select the defective cell is input to the memory device, a redundancy line used to select the redundancy cell is accessed instead of the defective line.
A typical repair process is designed to cut or blow a fuse. However, since a method for repairing a semiconductor device by blowing the fuse performs the repair process on a wafer level, it cannot be applied to a packaged semiconductor device. In addition, as an integration degree of the semiconductor device gradually increases, a spot size of a laser beam required for the fuse cutting may be larger than a pitch of the fuse, so that it is impossible to perform the repair process using the fuse cutting. Therefore, a new method to overcome the limitations of the above-mentioned repair method using an anti-fuse has been introduced.
The method using the anti-fuse can perform a program operation capable of easily repairing a defective cell in the packaged memory device. An anti-fuse starts with a high resistance and is designed to create an electrically conductive path typically when a voltage across the anti-fuse exceeds a certain level, whereas a fuse starts with a low resistance and is designed to break an electrically conductive path typically when a current through the path exceeds a specified limit. Generally, the anti-fuse is formed with a very thin dielectric layer of a non-conducting amorphous material between two electrical conductors.
In accordance with a program operation of the anti-fuse, a predetermined voltage is applied to the anti-fuse during a sufficient period of time such that the dielectric layer located between two conductors is broken down to program the anti-fuse. Accordingly, the anti-fuse is electrically opened in a basic status. If the anti-fuse is programmed upon receiving a high voltage, it is electrically short-circuited.
However, as the semiconductor device is highly integrated, the anti-fuse is also highly integrated.